Ball End Mill Troubles

[drafting3]

Absolute machining noob issue here, i'm sure.

 

 

I recently had a project where I was basically machining a 1" radius half-pipe shaped channel out of 1018.

 

I decided to rough this out with a ball end mill. (mistake?)

 

Using a 3/4" 4-flue cobalt ball end mill, step down of .200, speed 560, feed 4.0.

 

 

The cutter makes it about 2" into the first cut (slotted width at this point because it is the first cut) and burns up. The part and the cutter are glowing red from underneath a constant flood of coolant.

 

E-Stop.

End Mill ruined.

Load in a piece of carbide to clear the wreckage.

 

Someone mentioned chip clearance being an issue, so I switched to a 3/4" 2-Flute HSS ball end mill, and made no changes to the speed and feed. After that it cut fine. No problems, even without lowering the feed to take into account fewer flutes.

 

 

I've had other issues with this type of cut with a 4-flute ball end mill. Should I just avoid using 4-flutes for this type of slotted ball cut? Should I raise/lower my feed?

[K2csq7]

4 flutes & full slotting rarely produce good results.

By the sounds of your part you should be roughing with a different tool... Got any insert mills laying around?

Save the ball for finish...

[EX-wccprogrammer]

Rough with a flat endmill, leave stock for the radius. Then finish with the ball. My personal preference for roughing is variable helix carbide, but insert mill is a viable option.

[EX-wccprogrammer]

With a Varimill, 3/4 dia full slot.... in 1018 can run .750 depth of cut, 3050 rpm at 43.0 feed.

[drafting3]

thanks guys.

 

i chose to rough with a BEM because using a flat endmill left large chunks of material to be machined on my finish pass.

 

just leave it that way and let the BEM hog out those areas, or should I add another rough operation before my finish to remove those areas?

[EX-wccprogrammer]

Use a smaller dia flat tool to take some out. A 3/8 Varimill would get most of the stress off of the tip of the ball in one pass. In 1018 could run at 6100 rpm at 39.0 feed.

[EX-wccprogrammer]

Oh, and when I say Varimill, that happens to be the brand name that I have most experience with. There are other brand names that will provide similar performance. Variable helix is the important feature.

[drafting3]

Oh, and when I say Varimill, that happens to be the brand name that I have most experience with. There are other brand names that will provide similar performance. Variable helix is the important feature.

 

thank you, sir.

[K2csq7]

If you will be doing stuff like this regularly, look into a feedmill.

They are made to take light DOC passes at ridiculously high feedrates, they have large corner rads which would blend nicely to a curved surface therefore wont leave the "huge chunks" you talked about.